Alkali-refining of fatty glycerides in the presence of an inorganic phosphate compound



name no a mo 2,507,134

UNITED STATES PATENT OFFICE ALKALI- EFINING F FATTY GLYCERIDES IN THE PRESENCE OF AN INORGANIC PHOSPHATE OOMPOUND 8. Jack Winchester. Mala, r to Le Brothen company, Dominiowans. a ox: notation of Maine No Drawing. Application May 28, 1948, Serial No. 30,178

1 7 Claims. (01. 260-425) 2 This invention relates to the alkali-refining oi bodiments of the invention are set forth hereinfatty giyceride stocks in the presence of a small m,- amount of an inorganic phosphate compo nd. In order to facilitate a clear understanding of and especia ly in one embodiment to the alkalithe invention, the following specific embodiments refining of soybean oil in the presence of a small 5 are t forth,

amount of tetrasodium pyrophosphate.

The alkali-refining of fatty glyceride stocks EXAMPLE 1 has long been practiced, an extensive informa- To a batch of degummed, solvent extracted tion as to procedural details is available in the soybean oil having 0.3% free fatty acid by weight literature; e. g., "Industrial Oil and Fat Prodon the 011, there is added 0.10% of tetrasodium H ts. by Al a Interscience Publishers, pyrophosphate (NmPzOv) based on the weight of Inc., New York, N. Y., 1945, which described rethe oil, and in the form of a 10% aqueous solufining process, among others, that one charactertion, at room temperature and with agitation. ized as the "dry method and the "wet" method; Then there is added sodium hydroxide in an "Vegetable Fats and Oils," by George S. Jamiel5 amount of 0.2% in excess of the stoichiometric son, Reinhold Publishing Corporation, New York, amount required for neutralization of the free 1943. Generally, alkali-refining involves difatty acids in the oil, in the form of a 16 B. lye phasic separation of an aqueous phase containsolution, at room temperature and with agitation ing undesirable impurities, and a refined oil (in accordance with usual procedures). Agitaphase. The phases may be allowed to separate 20 tion is continued for 15 minutes. Then the tem by gravity, as in kettle refining, or may be sepaperature of the reaction mixture is raised to about rated by centrifugal means. 52 C., with continued agitation. Agitation is The art is confronted with th problem of stopped and the batch is allowed to settle for 8 minimizing refining losses, which are a serious hours. The refined oil is removed from the setfactor in the large scale refining processes, espetied foots. e. y means 8- skim P pe (in cially in batch or kettle refining, Th rt r accordance with the usual dry method). The gards the presence of organic surface active comresulting refining 1058 is (all refining 105888 pounds in the oils, e. g., phosphatides in soybean herein are on an anhydmus Weight basis- "111885 oil, among other factors, as being associated with otherwise indicate!)- This is to e compared high reflmng losses; with an alkali-refining loss for this oil of higher In accordance with the invention, it has been than 3 Similarly refined except WithOut found that the refining losses may be markedly adding any M the pymphosphate- The resulting reduced if the alkali-refining is carried out in the Oduct is of satisfactory quality, e. g., for bleachpresence of an Inorganic phosphate compmmm ing with i'ullers earth or with acid activated This invention is of great commercial sigmm a clay, and further processing toprepareashortencance, inasmuch as it permits alkali-refining in in large scale conventional kettles with relatively low EXAMPLE 2 losses, e. g., comparable to those obtained by more costlycentrifugal methods, to give a result- Following the procedure of Example except ing product "of satisfactory quality The pres- 40 with an on having 05% free fatty acid using a course, the diil'erence is not so marked since the loss is obtame The roots i is heavy and losses in the centrifugal Process are already tight, and tends to settle out very rapidly. The

tively lower. resulting product is of satisfactor ualit The objects achieved in accordance with the y q y invention include the provision of methods or EXAMPLE 3 alkalireflning fatty glycerides with relatively low This example uses the same on and follows refining losses, wherein the reflningis carried out the procedure of Example 1 except t the in the presence of an inorganic phosphate com- 1 is heated to t t tetrasodium pypound; the provision of processes of alkali-rerophosphate solution is added, and then the lye fining soybean oil in the presence of a small is added, all with agitation. Then the mixture amount of tetrasodium pyrophosphate; and other is rapidly agitated for 5 minutes to mix the inobjects which will be apparent as details or am sbgredients thoroughly, and then agitated for 5 more minutes with medium agitation at a speech prevent the foots particles from dropping. Then agitation is stopped and a to hot is sprayed on the oil; and the mixto settle without agitation for 3 The relatively clear portion of the aqueous phase is withdrawn from the bottom (in accordance with the usual wet" method); a second (about 5%) hot water wash is applied to the oil, and the mixture is allowed to settle for 1% hours, after which the relatively clear portion of the aqueous phase is withdrawn. Then a third (about 5%) hot water wash is applied, the mixture is allowed to settle for 1 hour, and then all the aqueous phase is withdrawn. A refining loss of 0.56% is obtained, and the resulting product is of satisfactory quality.

EXAMP 4 In a repeat run, following the procedure of Example 3, except with an oil having 0.5% free fatty acid, a refining loss of 0.96% is obtained, and the product is of satisfactory quality.

EXAMPLE 5 degummed solvent extracted as in Example 1), there is added 0.1% of tetrasodium py ophos- 10% aqueous solution, following which there is added sodium hydroxide in an amount 0.2% in excess of the stoichiometric amount required for neutralization of the free fatty acids in the oil, in the form of a 16 Be. lye solution. Both the phosphate and lye are at room temperature, with rapid agitation which is continued for 0 minutes after adding the lye; then the temperature is raised to 10 C. with lust sufficient agitation to keep the foots particles from dropping to the bottom. The agitation is then stopped and the process continued as described in Example 3. A refining loss of 0.62% is obtained; and the product is of satisfactory quality.

EXAMIPLE6 To a batch of extracted degummed soybean oil having0.l7% free fatty acid there is added about 1.85% by volume of a saturated solution or tetrasodium pyrophosphate (at room temperature). and then there is added 2.9% by volume of 6 Be. lye, with agitation at 40 C. The oil may be heated to 80 C. before adding the pyrophosphate and the lye, or after adding both, or intermediate the addition of these two agents. After heating to 80 0., the resulting mixture is settled, and washed by a 10% by weight still water wash. After again settling, the aqueous phase is removed (wet" method). In this way a refining loss of 0.4% is obtained, and the product is of satisfactory quality. This is to be compared with a refining loss of 1.7% for the same oil refined in the same manner, except without adding any tetrasodium pyrophosphate.

EXAMPLE '7 Following the procedure of Example 6, except usin an expeller soybean oil having about 0.5% free fatty acid, and using about 4.0% by volume of 0'' as. lye, a refining loss of 2.1% is obtained, and the product is of satisfactory quality. This is to be compared with a refining loss of 14.1% for the same oil refined in the same way, except without any tetrasodium pyrophosphate.

This reduction in loss is indeed surprising when one considers that the pyrophosphate is a surface active material, and that the soybean oil already ill contains surface active phosphatide material. This oil presents particularly difficult refining discovery of the process of alsodium pyrophosphate is a much desired advance therein. The above examples represent the preferred embodiment of the invention and that which is of the greatest commercial significance at this time.

The following examples and discussions illustrate or show broader aspects of the inventio e. g., as applied to other oils and fats or as to the use of other inorganic phosphate additives. Although tetrasodium pyrophosphate is markedly superior in many instances, other inorganic phosphates may be used to show some improvement as indicated below.

EXAMPLE-8 To a batch of cottonseed oil having 2.0% free fatty acid, there is added about 0.1% of tetrasodium pyrophosphate (as an aqueous solution saturated at room temperature), and then there is added sodium hydroxide in an amount 0.5% in excess of the stoichiometric amount required for neutralization of free fatty acid in the oil, in the form of a 12 B. lye solution, all at C. and with rapid agitation for 5 minutes. Then the mixture is settled, and given two still washes with hot water, and after settling the aqueous layer is removed. A 7.8% refining loss is obtained, and the product can be bleached and further processed in the conventional manner. This is to be compared with a refining loss of 12.6% for the same oil refined in the same manner, except without any tetrasodium pyrophosphate.

EXAMPLEQ A batch of expeller soybean oil having an 0.4% free fatty acid content, is treated with 1.85% by volume of a solution (saturated at room temperature) of trisodium phosphate. There is then added at 40 C. a 12 B. lye solution in an amount to provide 0.23% sodium hydroxide in excess of that required to neutralize the free fatty acids. The foots settled down well and left a clear oil, the refining loss being 1.1% as compared with a loss of 8.2% when the phosphate is not used.

EXAMPLES 10-17 A series of phosphate compounds were used as additives in alkali-refining and expeller soybean fatty acid content of 0.62%, and also an extracted, degummed soybean oil having a free fatty acid content of 0.42%. The Glass Kettle Method was used, except that the foots were not finally centrifuged. This method, and the apparatus used for practicing it, is described in Oil and Soap,-vol. 22, page 158 (1945). The alkali was 8 B. and used in 0.2% excess and the phosphate additives were all in a 10% aqueous solution and the amount and nature of the phosphate and the refining loss is indicated in the following tables:

Expeller soybean oil Example No. Additive gag Per cent is. a, a s a o 4.1 0.1

5 Extracted depummcd soybean oil Example No. Additive ,{fgfg Per cent Nona. 3. 4 64150:... 0.0 I, NA PIOmn- 1.9 .i il:P0 1.4 .l (NaPO:)|.. 0. 46

to the oil prior to the alkali.

Following the usual alkali-refining procedures as applied to known fats and oils (e. g., as described in the literature), especially vegetable oils, refining losses may be reduced substantially by including a, small amount of water-soluble inorganic phosphate compound, preferably one which is surface active. In general, the amount of the phosphate compound should be sufilcient to reduce the refining loss, and not so large etc. as to increase it. An amount up to about 0.75% and preferably in the range of about 0.05% to about 0.5% by weight, calculated as anhydrous, and based on the weight of the oil, will generally be suitable. The use of mixtures of the phosphate compounds is included in the invention. Instead the sodium compounds, soluble or dispersible compounds containing other cations, especially the alkali metals, may be used. Generally, the sodium compounds are to be preferred for economic reasons.

In view of the foregoing disclosures, variations and modifications thereof will be apparent to those skilled in the art, and the invention contemplates all such variations and modifications except as do not come within the scope of the appended claims.

I claim:

1. In a process of alkali-refining a fatty glyceride stock by treatment with aqueous alkali, as the essential neutralizing agent for free fatty acids in the stock and separating an aqueous phase containing undesirable impurities and a refined oil phase, the improvement which comprises having present in the refining mixture a small amount up to about 0.75% of an inorganic phosphate compound to reduce the refining losses.

2. The process of claim 1, wherein the phases are formed into separate layers by settling.

3. The process of claim 2, wherein the aqueous phase is drawn on from below the oil phase.

4. The process of claim 1, wherein the fatty glyceride is a soybean oil.

5. The process of claim 1, wherein the phosphate compound is tetrasodium pyrophosphate.

6. The process of claim 1 in which the phosphate is added to the oil as a. solution before the alkali is added.

7. The process of claim 1 in which the phosphate is added in an amount within the range of 0.05% to 0.5%.

8. JACK RINI.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,115,668 James Apr. 96, 1938 2,190,594 Clayton Feb. 13, 1940 

1. IN A PROCESS OF ALKALI-REFINING A FATTY GLYCERIDE STOCK BY TREATMENT WITH AQUEOUS ALKALI, AS THE ESSENTIAL NEUTRALIZING AGENT FOR FREE FATTY ACIDS IN THE STOCK AND SEPARATING AN AQUEOUS PHASE CONTAINING UNDESIRABLE IMPURTIES AND A REFINED OIL PHASE, THE IMPROVEMENT WHICH COMPRISES HAVING PRESENT IN THE REFINING MIXTURE A SMALL AMOUNT UP TO ABOUT 0.75% OF AN INORGANIC PHOSPHATE COMPOUND TO REDUCE THE REFINING LOSES. 